Exhaust gas purification utilizing a clutch to switch between driving forces in a hybrid vehicle

The present application claims priority to Japanese Patent Applications number 2023-024797, filed on Feb. 21, 2023. The contents of this application are incorporated herein by reference in their entirety.

There are known technologies by which an exhaust gas purification device, for collecting soot in exhaust gas discharged from an engine, is regenerated when it is detected during traveling of a vehicle that soot has accumulated in the exhaust gas purification device. For example, Japanese Unexamined Patent Application Publication No. 2017-178006 discloses that an engine and a motor generator become disengaged when a clutch connecting the engine and the motor generator is disconnected. Japanese Unexamined Application Publication No. 2017-178006 discloses that when the engine and the motor generator are disconnected for such a specific reason, and a vehicle is in a solely-running-on-motor state, during which the vehicle travels on a driving force generated by the motor generator, the retarder is activated, and engine combustion is engaged. This enables regeneration of the exhaust gas purification device by increasing a temperature of the exhaust gas flowing into the exhaust gas purification device through engagement of the engine combustion and activation of the retarder to apply a load to the engine.

However, a driving force generated by the engine is not used to cause traveling of the vehicle during the regeneration of the exhaust gas purification device in the method described in Japanese Unexamined Application Publication No. 2017-178006, and therefore there is a reduction of fuel efficiency of the vehicle.

The present disclosure focuses on this point, and its object is to provide a vehicle capable of suppressing a reduction of fuel efficiency of the vehicle when an exhaust gas purification device is regenerated during traveling of the vehicle.

A vehicle according to an aspect of the present disclosure includes: an electric motor that generates a first driving force for rotationally driving drive wheels of the vehicle; an engine that generates a second driving force for rotationally driving the drive wheels of the vehicle; an exhaust gas purification device that purifies exhaust gas generated in the engine; a generator that generates electric power using the second driving force; and a clutch that switches whether or not to transmit the second driving force to the drive wheels, wherein when the second driving force is not being transmitted to the drive wheels, the engine operates at a higher rotational speed than when the second driving force is being transmitted to the drive wheels, and the electric motor generates the first driving force using the electric power generated by the generator by using the second driving force.

Hereinafter, the present disclosure will be described through exemplary embodiments, but the following exemplary embodiments do not limit the invention according to the claims, and not all of the combinations of features described in the exemplary embodiments are necessarily essential to the solution means of the invention.

[Outline of a Vehicle]

shows a configuration of a vehicleaccording to the present embodiment. The vehicleincludes an engine, an exhaust gas purification device, an after-treatment device, a generator, an electric motor, a transmission, a differential gear, a plurality of drive wheels, a first clutch, a second clutch, a first pressure sensor, a second pressure sensor, a battery, and a vehicle controller. In the example of, the vehicletravels by having the engineand the electric motorrotate the drive wheels. Outside air drawn into the vehicle passes through the engine, the exhaust gas purification device, and the after-treatment devicein this order, and is discharged to the outside.

The enginegenerates an engine driving force (corresponding to a second driving force) for rotationally driving the drive wheelsof the vehicle. The exhaust gas purification devicepurifies exhaust gas generated in the engine. For example, the exhaust gas purification deviceincludes a DPF (Diesel Particulate Filter) for collecting soot in the exhaust gas, and a DOC (Diesel Oxidation Catalyst) provided in the stage preceding the DPF, for example. The exhaust gas purification devicemay include an SCR (Selective Catalytic Reduction) catalyst.

The after-treatment deviceincludes the SCR catalyst, for example. The after-treatment devicereduces nitrogen oxides in the exhaust gas.

The generatorgenerates electric power by using the engine driving force generated by the engine. The generatoris provided in or around a flywheel of the engine, for example. The generatormay also operate as an electric motor.

The electric motorgenerates an electric driving force (corresponding to a first driving force) for rotationally driving the drive wheelsof the vehicle. The electric motorassists the engine driving force generated by the engine. The electric motorcan cause the vehicleto travel only by the generated electric driving force. The electric motormay also operate as a generator. For example, the electric motormay operate as a regenerative brake during braking to generate electric power.

By changing a combination of gears, the transmissionincreases a torque generated by the engineand transmits the increased torque to the differential gearand the drive wheels. The differential gearcauses the drive wheelsthat are on the outer side to rotate relatively quickly and the drive wheelsthat are on the inner side to rotate relatively slowly when the vehicleturns.

The first clutchis provided between the generatorand the electric motor. The first clutchswitches between (i) an ON state in which the engine driving force generated by the engineis transmitted to the drive wheelsof the vehicleand (ii) an OFF state in which said engine driving force is not transmitted to the drive wheels. The second clutchswitches between (i) an ON state in which the electric driving force generated by the electric motorand the engine driving force are transmitted to the drive wheelsof the vehicleand (ii) an OFF state in which the electric driving force and the engine driving force are not transmitted to the drive wheels.

The first pressure sensormeasures a first pressure of the exhaust gas before passing through the exhaust gas purification device. The first pressure sensorinputs the measured first pressure to the vehicle controller. The second pressure sensormeasures a second pressure of the exhaust gas after passing through the exhaust gas purification device. The second pressure sensorinputs the measured second pressure to the vehicle controller.

The batterystores the electric power generated by the generator. The batterysupplies the stored electric power to the electric motor. The vehicle controllerincludes a processor. The vehicle controllerincludes an HEV (Hybrid Electric Vehicle) controller, for example. The vehicle controllerexecutes a power generation process performed by the generatorand a process of assisting the enginewith the electric motor, for example.

In the exhaust gas purification device, purification performance of the exhaust gas gradually decreases due to soot being accumulated. In order to regenerate the exhaust gas purification device, in which soot is accumulated, during traveling of while the vehicle, the vehicle controllerfirst switches the first clutchto the OFF state in which the engine driving force is not transmitted to the drive wheels. The vehicle controllersupplies the electric power generated by the generatorto the electric motorwith the first clutchin the OFF state, and causes the vehicleto travel on the electric driving force generated by the electric motor. At this time, the vehicle controllerincreases a temperature of the exhaust gas by increasing the rotational speed of the engineas compared to when the first clutchis in the ON state in which the engine driving force is transmitted to the drive wheels.

In this way, by increasing the temperature of the exhaust gas, the vehicle controllercan incinerate the soot collected by the exhaust gas purification device. Therefore, the vehicle controllercan suppress a reduction of removal performance of carbon dioxide, nitrogen oxides, or the like due to the accumulation of soot in the exhaust gas purification device. Since the vehicle controllergenerates electric power in the generatorby using the engine driving force of the enginewhose rotational speed is increased in order to increase the temperature of the exhaust gas, and reuses the electric power with the electric motor, it is possible to suppress a reduction of fuel efficiency of the vehicleat the time of incinerating the soot collected by the exhaust gas purification device.

[Configuration of Main Parts of the Vehicle]

shows a configuration of main parts of the vehicle. The vehicleincludes the first pressure sensor, the second pressure sensor, a fuel injection device, the first clutch, the generator, the electric motor, and the vehicle controller. The vehicle controllerincludes a storageand a control part.

The fuel injection deviceinjects fuel into a cylinder of the engine. The fuel injection deviceinjects an injection amount of fuel instructed by the control partinto the cylinder of the engine. The storageincludes a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, for example. The storagestores various types of programs for causing the control partto function and various types of data.

The control partis a processor mounted on the vehicle controller, for example. The control partexecutes various functions by executing the programs stored in the storage. The control partacquires information indicating the first pressure measured by the first pressure sensor. The control partacquires information indicating the second pressure measured by the second pressure sensor. The control partcalculates a pressure difference between the acquired first pressure and second pressure. This pressure difference is a difference that arises because, when soot accumulates in a filter of the exhaust gas purification device, it hinders the smooth passage of the exhaust gas through the exhaust gas purification device. The greater the amount of soot accumulated, the larger this pressure difference becomes.

Although details will be described later, the control partincinerates the soot accumulated in the exhaust gas purification deviceon the basis of the calculated pressure difference. For example, if the pressure difference is equal to or greater than a threshold value, the control partincreases the engine speed by increasing the amount of fuel injected by the fuel injection device. The control partincinerates the soot accumulated in the exhaust gas purification deviceby increasing the engine speed. Hereinafter, a regeneration process of the exhaust gas purification devicewill be described for each situation of the vehicleduring regeneration.

[Case where the Regeneration of the Exhaust Gas Purification Deviceis not Performed]

If the acquired pressure difference between the first pressure and the second pressure is less than a combustion threshold value or less than a preparation threshold value, the control partdoes not incinerate the soot accumulated in the exhaust gas purification device. The combustion threshold value is determined as a value corresponding to a period required for incinerating the soot collected in the exhaust gas purification device, for example. The preparation threshold value indicates a value smaller than the combustion threshold. If the acquired pressure difference between the first pressure and the second pressure is less than the combustion threshold value or less than the preparation threshold value, the control partswitches the first clutchto the ON state in which the engine driving force is transmitted to the drive wheels, and rotationally drives the drive wheelswith both the electric driving force and the engine driving force. The control partoperates the second clutchin the ON state in which the electric driving force generated by the electric motorand the engine driving force are transmitted to the drive wheelsof the vehicle.

[Case where the Regeneration of the Exhaust Gas Purification Deviceis Performed]

If it is determined that the pressure difference between the first pressure and the second pressure is equal to or greater than the combustion threshold value during traveling of the vehicleor during a stoppage of the vehicle, the control partincinerates the soot, which is accumulated in the exhaust gas purification device, during idling or traveling of the vehicleaccording to a driving operation of a driver. First, an example in which the control partincinerates the soot accumulated in the exhaust gas purification deviceduring the idling of the vehiclewill be described.

[Case where the Regeneration of the Exhaust Gas Purification Deviceis Performed During the Idling]

In the case of incinerating the soot accumulated in the exhaust gas purification deviceduring the idling, the control partswitches the first clutchto the OFF state in which the engine driving force is not transmitted to the drive wheels, and increases the rotational speed of the engineto a greater degree than when the first clutchis in the ON state in which the engine driving force is transmitted to the drive wheels. The control partincreases the temperature of the exhaust gas from the engineby increasing the rotational speed of the engine. At this time, the control partcauses the generatorto generate electric power by using the engine driving force, and supplies the electric power to the battery. If the control partis connected to an external device such as household electric equipment or electric storage equipment via a converter, the control partmay supply the electric power generated by the generatorto the external device, instead of supplying this electric power to the battery.

[Case where the Regeneration of the Exhaust Gas Purification Deviceis Performed During Traveling]

In the case of incinerating the soot accumulated in the exhaust gas purification deviceduring traveling of the vehicle, the control partswitches the first clutchto the OFF state in which the engine driving force is not transmitted to the drive wheels, and causes the vehicleto travel on the electric driving force. While the vehicleis traveling on the electric driving force with the first clutchbeing in the OFF state, the control partincreases the temperature of the exhaust gas from the engineby increasing the rotational speed of the enginemore than when the first clutchis in the ON state in which the engine driving force is transmitted to the drive wheels. The control partcauses the generatorto generate electric power by using the engine driving force, and supplies the electric power to the electric motor. At this time, the control partoperates the second clutchto be in the ON state in which the electric driving force generated by the electric motoris transmitted to the drive wheels.

[Case where the Regeneration of the Exhaust Gas Purification Deviceis Performed after the Battery Level has been Lowered]

The control partincreases the engine speed during incineration of the soot collected by the exhaust gas purification device. At this time, as the engine speed increases, the amount of electric power generated by the generatoralso increases. To secure available capacity for storing said electric power in the battery, the control partmay consume electric power stored in the batterybefore incinerating the soot collected by the exhaust gas purification device.

If it is determined that the pressure difference between the first pressure and the second pressure is equal to or greater than a preliminary threshold value and less than the combustion threshold value during traveling of the vehicle, the control partincreases the ratio of rotationally driving the drive wheelswith the electric driving force, from among the engine driving force and the electric driving force, in comparison to the case where the pressure difference is less than the preliminary threshold value. The preliminary threshold value is less than the combustion threshold value. At this time, the control partswitches the first clutchto the ON state in which the engine driving force is transmitted to the drive wheels, and operates the second clutchto be in the ON state in which the engine driving force and the electric driving force are transmitted to the drive wheel. In this way, the control partcan increase the amount of power consumed by the electric motor.

Then, due to continued collection of soot by the exhaust gas purification device, the pressure difference between the first pressure and the second pressure gradually increases.shows change over time in the pressure difference between the first pressure and the second pressure. The vertical axis ofrepresents the pressure difference between the first pressure and the second pressure. The horizontal axis ofrepresents the vehicle operation time since the previous regeneration process of the exhaust gas purification device. As shown in, as the vehicle operation time increases, the pressure difference between the first pressure and the second pressure monotonously increases. In the example of, when the vehicle operation time is T1, the pressure difference between the first pressure and the second pressure is equal to the preliminary threshold value. When the vehicle operation time is T2, the pressure difference between the first pressure and the second pressure is equal to the combustion threshold value.

If it is determined that the pressure difference between the first pressure and the second pressure is equal to or greater than the combustion threshold value during traveling of the vehicle, the control partswitches the first clutchto the OFF state in which the engine driving force is not transmitted to the drive wheels. The control partcauses the vehicleto travel on the electric driving force with the first clutchbeing in the OFF state. At this time, as described above, the control partincinerates the soot collected by the exhaust gas purification deviceby increasing the rotational speed of the engine.

shows change over time of the battery level of the battery. The vertical axis inindicates the battery level of the battery. The horizontal axis ofrepresents the vehicle operation time. In the example of, the battery level at the vehicle operation time T1, (see) at which the pressure difference between the first pressure and the second pressure becomes equal to the preliminary threshold value, is E1. At this time, the control partgradually lowers the battery level by making the electric driving force larger than the engine driving force, among the electric driving force and the engine driving force for rotationally driving the drive wheels.

In the vehicle operation time T2 in which the pressure difference between the first pressure and the second pressure becomes equal to the combustion threshold value, the battery level becomes E2, which is lower than E1. At this time, the control partincreases the amount of electricity generated by the generatorby increasing the rotational speed of the enginein comparison to when the first clutchis in the ON state. In the example of, the generated electricity amount after it has been increased is greater than the amount of power consumed by the electric motor. Therefore, while the control partincreases the rotational speed of the engine, the battery level (State of Charge, for example) is gradually increased.

[Processing Procedure for Regenerating the Exhaust Gas Purification DevicePerformed by the Vehicle Controller]

is a flowchart showing a processing procedure for regenerating the exhaust gas purification deviceperformed by the vehicle controller. This processing procedure starts when the vehicleis traveling, for example. First, the control partacquires information indicating first pressure of the exhaust gas before passing through the exhaust gas purification device, from the first pressure sensor. The control partacquires information indicating second pressure of the exhaust gas after passing through the exhaust gas purification device, from the second pressure sensor(S).

The control partcalculates a pressure difference between the first pressure and the second pressure. The control partdetermines whether or not the calculated pressure difference is less than a preliminary threshold value (S). If it is determined that the pressure difference is equal to or greater than the preliminary threshold value (NO in S), the control partdetermines whether the pressure difference is equal to or greater than a combustion threshold value (S). If the pressure difference is equal to or greater than the combustion threshold value (YES in S), the control partswitches the first clutchto the OFF state in which an engine driving force is not transmitted to the drive wheels(S), and causes the vehicleto travel on the electric driving force (S).

The control partincinerates soot collected by the exhaust gas purification deviceby increasing a temperature of the exhaust gas from the engineby increasing the rotational speed of the engineas compared with when the first clutchis in the ON state in which the engine driving force is transmitted to the drive wheels(S). The control partcauses the generatorto generate electric power by using rotation of the engine(S). The control partdetermines whether or not the traveling of the vehiclehas ended (S). If it is determined that the traveling of the vehiclehas ended (YES in S), the control partends the process.

If it is determined that the pressure difference is less than the preliminary threshold value in the determination in S(YES in S), the control partproceeds to the determination of S. If it is determined that the pressure difference is less than the combustion threshold value in the determination in S(NO in S), the control partincreases the ratio of rotationally driving the drive wheelswith the electric driving force, from among the engine driving force and the electric driving force for rotationally driving the drive wheels, in comparison to the case where the pressure difference is less than the preliminary threshold value (S), and proceeds to the determination of S. If it is determined that the traveling of the vehiclehas not ended in the determination in S(NO in S), the control partreturns to the process in S.

[Effect of the Vehicle Controllerof the Present Embodiment]

The control partcan incinerate the soot collected by the exhaust gas purification deviceby increasing the temperature of the exhaust gas. Therefore, the control partcan suppress a reduction in the removal performance of carbon dioxide, nitrogen oxides, or the like caused by the exhaust gas purification device. Since the control partgenerates electric power in the generatorby using the engine driving force of the enginewhose rotational speed is increased in order to increase the temperature of the exhaust gas, and reuses the electric power by the electric motor, it is possible to suppress the reduction of fuel efficiency of the vehicleat the time of incinerating the soot collected by the exhaust gas purification device.

The present disclosure is explained on the basis of the exemplary embodiments. The technical scope of the present disclosure is not limited to the scope explained in the above embodiments and it is possible to make various changes and modifications within the scope of the disclosure. For example, all or part of the apparatus can be configured with any unit which is functionally or physically dispersed or integrated. Further, new exemplary embodiments generated by arbitrary combinations of them are included in the exemplary embodiments. Further, effects of the new exemplary embodiments brought by the combinations also have the effects of the original exemplary embodiments.